Access technologies of various kinds, especially wireless, are becoming increasingly ubiquitous, e.g. in the shape of GSM/GPRS/EDGE, WCDMA/HSPA, CDMA2000, WLAN, WiMAX and soon LTE (EDGE is an abbreviation for “Enhanced Data Rates for GSM Evolution”; GPRS for “General Packet Radio Service”; GSM for “Global System for Mobile communication”; WCDMA for “Wideband Code Division Multiple Access”; HSPA for “High Speed Packet Access”; WLAN for “Wireless Local Area Network”; WiMAX for “Worldwide Interoperability for Microwave Access”; and LTE for “Long Term Evolution”; while CDMA2000 is a CDMA based 3 G [3rd Generation] standard for cellular networks). The mobile terminals match this multitude of access technologies by including ever more access interfaces to allow greater freedom and flexibility in the selection of access to use for each communication session.
To leverage the benefits of this growing flexibility it becomes important to have mechanisms in place for efficient control of the access selection, to ensure that a mobile node always uses its available access interfaces and access networks as efficiently as possible for the currently ongoing communication sessions. Circumstances to take into account include e.g. the currently used applications, access network technologies and their properties, access network operators (and their relations to the user's home operator), current network conditions (e.g. load), location, subscription restrictions, time of day, etc. Similarly, it is desirable to support a mobile node in discovering available accesses without requiring the mobile node to continuously scan for all accesses and thus using battery resources.
In SAE/LTE, also known as EPS (Evolved Packet System), i.e. the future evolved 3GPP system, multi-access is a key element. Control of access selection (and access discovery) is recognized as an important aspect and has been assigned a dedicated work item.
The mechanisms considered are based on policies and/or rules. The functionality provided by a policy/rule is instructions or guidance of which access to select or how to discover accesses given the specific circumstance (device context).
The exact definitions of policies and rules and their precise relation are somewhat up in the air and the notion of this varies between different people. The standardization organizations 3GPP (3rd Generation Partnership Project) and IETF (Internet Engineering Task Force) are both working in the area. One view is that a policy expresses preferences or obligations on a higher level, whereas rules are lower level structures, which can be derived from policies, providing more detailed instructions for the access selection in a stricter format, e.g. pointing out a certain access network or access interface. In the background chapter the two volatile terms are mixed, partly because the text may apply to both terms, even in case their definition differs. However, in the actual description of the inventive solution only the term rule is consistently used.
Policies and/or rules may be processed in the network, e.g. in the Policy and Charging Rules Function (PCRF) or, in the context of access selection, more likely in the newly introduced functional entity Access Network Discovery and Selection Function (ANDSF), which is responsible for access selection between 3GPP accesses and non-3GPP accesses as well as between different non-3GPP accesses. The ANDSF is distributed between the mobile node (ueANDSF) and the network. In the network the ANDSF is located both in the home network (hANDSF) and in the visited network (vANDSF). The network based ANDSF will probably be located in an entity inside (i.e. as an integral part of) or “near” the PCRF. It is also possible that there will be ANDSF related functionality in non-3GPP access networks, e.g. for provision of access properties as input data to the access selection process. Such possible ANDSF related functionality in non-3GPP access networks is herein tentatively labeled n3aANDSF. The introduction of the ANDSF in the 3GPP SAE architecture, as well as the most basic related information flows, are illustrated in FIG. 1. PDN stands for Packet Data Network. ANDSR stands for Access Network Discovery and Selection Rule. ePDG stands for evolved Packet Data Gateway. HSS stands for Home Subscriber Server. VoIP stands for Voice over IP.
Processing of policies and rules in the ANDSF may take place either in the network or in the mobile node (User Equipment or UE) or in both. The most likely scenario is that at least the final processing will take place in the mobile node (UE) where the access selection decision is executed. The mobile node (UE) communicates with the hANDSF, e.g. to receive policy and rule information. The vANDSF and the hANDSF may also communicate such information between each other, but a possible alternative is that the mobile node (UE) communicates directly with the vANDSF. FIG. 2 illustrates a possible architecture for policy and rule control.
For access selection between accesses that interwork on radio access network (RAN) level (e.g. different 3GPP accesses, such as LTE, WCDMA/HSPA and GERAN, and certain non-3GPP accesses, e.g. CDMA2000), the access selection functionality is network based and is typically located within the RANs (e.g. E-UTRAN, GERAN, UTRAN, CDMA2000-RAN, where E-UTRAN is “Evolved Universal Terrestrial Radio Access Network”, UTRAN is “Universal Terrestrial Radio Access Network” and GERAN is “GSM EDGE Radio Access Network”) and possibly partly also in the Mobility Management Entity (MME) and/or (Serving GPRS Support Node) SGSN (see FIG. 3). Potentially, processing of access selection related policies and rules may take place also in this access selection functionality.
It should be noted that herein ANDSF stands for “Access Network Discovery and Selection Function”, while aANDSF means ANDSF functionality in an access network, hANDSF means home ANDSF, n3aANDSF means ANDSF related functionality in non-3GPP access networks, ueANDSF means ANDSF functionality in the UE, and vANDSF means visited ANDSF. Similarly, while AN stands for Access Network, hAN is home Access Network, rAN is “roaming” Access Network, and vAN is visited Access Network. Similarly for hEPS (home EPS), vEPS (visited EPS), hPCRF (home PCRF), HPLMN (Home PLMN, where PLMN is Public Land Mobile Network), VPCRF (visited PCRF), and VPLMN (Visited PLMN).
FIG. 4 illustrates some access selection scenarios and examples of involved operators and cooperation constellations.
Access selection and access discovery are not restricted to mobile nodes/terminals. They are equally applicable for so called user networks. The term User Network (UN) refers to one or more inter-connected user devices that can access a network via one or more access technologies. Examples of a single-device user network are a cellular phone or a laptop, while an example of a multi-device user network is a Personal Area Network (PAN). In the context of 3GPP systems a device accessing the network is referred to as a UE (User Equipment). Although a UE is typically a single device, it may also consist of several devices constituting a UN.
There are several stakeholders in the process of access selection, e.g. the user, the home operator, operator of visited networks and providers of services. All stakeholders have an interest in the access selection and may want to influence its outcome. When several stakeholders provide rules to the ANDSF they may conflict with each other. Also there might be conflicts between rules from the same stakeholder when the applicability conditions for multiple rules are fulfilled, e.g. one rule that is applicable during a certain time (e.g. busy hour) and another rule that is applicable in a certain location or for a certain service. Existing solutions provide no method to resolve such conflicts.
It is desirable to provide a way to control selection and discovery of accesses for a mobile node in a multi-access system.